They don't affect your ride at all since they don't touch the axle when you're unloaded. Once you load up, and the rear squats, the bumpstops rest on the axle. I got the bumpstops for two reasons:
1. To keep my tires from being pushed up into my fenders when off-roading.
2. To keep my Trailblazer from squatting so far that my fenders pretty much ride on my tires when towing our mixtank.
They helped, but since I'm lifted, with bigger tires, they aren't quite long enough to do what I want. I'm planning on bolting a puck in the axle cup where the bumpstops are supposed to rest. That way, they'll make contact earlier and start doing their job sooner.
You can see the bumpstops resting in the cups on the axle. This is what they're supposed to do while towing or loaded.
This is while towing the mixtank when it's loaded. The Timbrens keep the fenders off the tires, but I'm going to put spacers in to get a little more clearance. If I wasn't lifted, and didn't have bigger tires, I don't think it would be a problem.